1. Field of Invention
The invention relates to low cost, reusable electric paper that uses a colored ferrofluidic fluid and is activated by an external magnetic writing instrument.
2. Description of Related Art
Reusable electric paper is described in U.S. Pat. Nos. 5,717,283 to Biegelsen, 5,723,204 to Stefik and 5,731,792 to Sheridon, all of which are incorporated herein by reference in their entirety. The 283 patent uses dielectric liquid in an array of hourglass-shaped pores. External electric fields move the liquid ink bistably from one volume to the other. See prior art FIG. 11. The 204 patent uses black and white spheres encapsulated in a liquid and embedded in a substrate. The spheres are responsive to an electrical field. The 792 patent uses encapsulated colored polar liquid and an electrode array embedded within a substrate to force the liquid to selected reservoirs to create an image on the substrate.